1. Field
The field of the invention relates to multimedia data, and more particularly to processing the multimedia data.
2. Background
Due to the explosive growth and great success of the Internet and wireless communication, as well as increasing demand for multimedia services, streaming media over the Internet and mobile/wireless channels has drawn tremendous attention. In heterogeneous Internet Protocol (IP) networks, video is provided by a server and can be streamed by one or more clients. Wired connections include dial-up, integrated services digital network (ISDN), cable, digital subscriber line protocols (collectively referred to as xDSL), fiber, local area networks (LAN), wide area networks (WAN) and others. The transmission mode can be either uni-cast or multi-cast.
Digital multimedia data can be transmitted such that users with properly configured remote devices can process the multimedia data. For example, the multimedia data can comprise video data to a remote device configured to view the transmitted video data images. In some systems, the source of the video data is analog, such as a broadcast television signal, or an analog cable signal. Before transmission, such analog signals are converted to digital frame information. The digital frame information includes the image data for each frame. To convert the analog video signal, to digital data for presentation to an end user, an encoder needs to generate timing information for the generated digital video frames. The digital frame information and the timing information are transmitted together so that a receiving device is provided with the video frames and the presentation timing needed to properly display the video images. The format of the timing information varies according to system protocols, and according to some system protocols, digital frame information is transmitted with presentation time stamps (PTS), which indicate times at which each digital frame is to be presented.
The digital frame information and the PTS information can be transmitted as a digital video signal such that it may be received by users with the proper receiving equipment, called a receiver. Receivers typically also function as decoders, decoding the received digital video signal to extract the digital frame information and the PTS information. The decoded information is presented to the user in a time sequence according to the PTS information. It is understood by those of skill in the art, that in some systems, such as some wireless networks, the reference clock is global to both the transmitter and the receiver. In some systems, as the PTS information was generated at the transmitter in accordance with a reference clock, the receiver correctly determines the time for each frame to be presented by using the same reference clock. Some systems may use a globally transmitted clock, such as a GPS clock or GPS derived clock, or other common master. Accordingly, the receiver extracts the digital frame information and presents the frame images on a display according to the timing information constructed from the PTS information based on the global reference clock.
Often the displays on receivers are awkwardly small and may have poor viewing quality. In some situations there is a desire or need for displaying the video information on an analog monitor, such as a television, which may be larger and have better display quality. Because the frame data and the timing data are in a format for the telecommunication system, and not for the analog monitor, the frame data and the timing data must be converted to a format compatible with the analog monitor, such as NTSC or PAL.